Weight for adjusting balance of a rotating body

ABSTRACT

A weight for adjusting balance of a rotating body obtained by adding and mixing one or two or more sorts of solid spherical powders selected from silicated glass, boro-silicated glass and phosphate glass to and with ultraviolet curing resin. The weight has improved specific gravity which is capable of sufficiently hardening even the inner part thereof without remaining an unhardened part in a short time only by being exposed to ultraviolet rays and suitable for a rotating body such as a rotor in a motor of a brushless outer rotor type or a brush motor and a polygon mirror for use in a laser printer because the powder particles thereof can be intimately bonded with one another through the adhesive resin.

RELEVANT TECHNICAL FIELD

This invention relates to an ultraviolet curing weight for adjusting thebalance of a rotating body, which is capable of adjusting the dynamicbalance of the rotating body, on rotating, such as a motor and a polygonmirror.

BACKGROUND OF THE ART

As a weight for adjusting the balance of a rotating body such as a rotorin a motor of a brushless outer-rotor type or a brush motor and apolygon mirror for use in a laser printer, there have been usedadhesives of epoxy resin singly or combined with powder having largespecific gravity such as metal powder.

Furthermore, the adhesives obtained by adding glass having largespecific gravity such as lead oxide, titanium oxide and barium oxide tothe ultraviolet curing resin have been allowed for. These adhesives(weight means) have been used in such a manner that they are filled in apart of the rotating body and hardened in order to adjust the balance ofthe rotating body.

However, in the case of using the singly composed adhesive as a weight,the quantity of the adhesive to be applied becomes increased because theadhesive alone is as small as about 1 in specific gravity. Thus, therecannot be secured room for accommodating the designated amount ofadhesive in a small-sized motor, and consequently, sufficient adjustmentof the balance of the rotor in the motor cannot be fulfilled.

The adhesive obtained by adding powder having large specific gravity toepoxy resin has also suffered a disadvantage such that the number ofprocesses for producing the adhesive of two-fluid mixing type isincreased because a mixing process is necessary therefor, and there is apossibility that the specific gravity of the adhesive is reduced due toair bubbles being possibly merged into the adhesive in the heatingprocess.

The adhesive of single-fluid type requires a heating process inproduction, and therefore, is unfavorable for mass-production. When anarticle to be supplied with the adhesive has plastic component parts,disadvantageously, it must be kept away from heat brought about in theheating process for hardening the adhesive.

In order to eliminate the aforementioned drawbacks, it has beenattempted to add lead oxide, titanium oxide, barium oxide or the like toan adhesive resin which is hardened by active-energy rays. However,ultraviolet curing resin alone has been generally used as a weight.Thus, such a resin adhesive is likely to become thinner on hardening andtakes much time to be hardened. Moreover, the resin adhesive entailed adisadvantage such that unhardened part of the adhesive applied to anobject still remains to unbalance the object, and adjustment of thebalance of the object becomes insufficient.

DESCRIPTION OF THE INVENTION

To solve the problems as mentioned above, the present invention providesa weight for adjusting the balance of a rotating body, which is obtainedby adding and mixing one or two or more sorts of solid spherical powdersselected from silicated glass, boro-silicated glass and phosphate glassto and with ultraviolet curing resin.

To the weight composition which is obtained by adding and mixing one ortwo or more sorts of solid spherical powders selected from silicatedglass, boro-silicated glass and phosphate glass to and with ultravioletcuring resin, there may be added one or two or more sorts of solidspherical powders selected from glass of TiO₂ --BaO--SiO₂ group, glassof BaO--ZnO--SiO₂ group and lead glass.

The ultraviolet curing resin used in this invention may include apolymerization initiator, a polymerization inhibitor, gum, elastomers, asilane coupling agent and/or a filler as occasion demands, other thanpolymeric oligomers and monomers polymerizable with ultraviolet rays.

As the polymeric oligomer as noted above, there may be used a compoundhaving at least one ethylene double bond structure capable ofpolymerizing. To put it concretely, there can be enumerated (meta)acrylates such as polyurethane (meta) acrylate, epoxy (meta) acrylate,polyester (meta) acrylate, and compounds denatured with vinyl group orallyl group.

As the polymerizable monomer as noted above, there can be enumeratedvinyl monomers such as (meta) acrylic esters, (meta) acrylamides,styrene and vinylpyrrolidone and allyl monomers such as allyl benzeneand allyl morpholine.

As the polymerization initiator as noted above, there can be enumerateda photopolymerization initiator such as benzophenone, diethoxyacetophenone, Michler's ketone, benzoin, benzoin alkyl ether,hydroxycyclohexyl ketone, benzil dimethylketal, thioxanthone anddiethyloxanthone, a polymerization initiator which is polymerized withheat produced by peroxides, and an anaerobic polymerization initiator.

The powder to be mixed with the ultraviolet curing resin in thisinvention may be selected from silicated glass, boro-silicated glass andphosphate glass which are high in permeability of ultraviolet rays andlarge in specific gravity so as not to exert a bad influence upon curingof the ultraviolet curing resin. To put it concretely, there can beenumerated silica glass, soda-lime glass and boro-aluminosilicatedglass.

The specific gravity of the powder is preferably 2.0 or more. It is moreimportant to make the powder solid, but not hollow, than the conditionas to the specific gravity.

Furthermore, the grain of the powder has to be shaped in a sphere inconsideration of light permeability, light non-directional property andcharging efficiency. In a case of the powder having disordered grainshapes such as fumed silica which has a non-spherical shape, the powdercannot be charged densely nor increased sufficiently in specificgravity.

The grain size of the powder is preferably about 5 to 500 μm taking thecharging efficiency and discharging property thereof into consideration.It is desirable to control the distribution of the grain size inconsideration of the viscosity, fluidity and charging efficiency.

The powder of glass of TiO₂ --BaO--SiO₂ group, glass of BaO--ZnO--SiO₂group or lead glass is required to be shaped in a sphere by the samereason as in the glass components as noted above.

In this case, though the powder of about 5 to 500 μm in grain size canbe used, the powder being small in grain size decreases itshardenability when forming a thick layer, and alternatively, the powderbeing large in grain size is difficult to restrain its precipitation.Thus, it is desirable to use the powder of about 40 to 200 μm in grainsize.

The powder of glass of TiO₂ --BaO--SiO₂ group, glass of BaO--ZnO--SiO₂group or lead glass is low in light permeability in comparison with theaforementioned spherical glass, resulting in a lowering of hardenabilitywhen resultantly forming a thick adhesive layer as a weight. However,these components are higher in specific gravity and light permeabilityin comparison with other possibly compositions having specific gravityequal to or higher than these components.

Therefore, when a space for accommodating the resultant adhesive in anobjective article is limited, the specific gravity of the weight can beincreased without impairing the hardenability of the thick adhesivelayer, by combining various glass compositions.

An arbitrary quantity of the powder may be added to and mixed with theadhesive. However, when the quantity of the powder to be added to theadhesive is insufficient, the effect of increasing the specific gravityof the weight cannot be produced, and alternatively, when the powder isadded to excess, the discharging property and adhesive property of theadhesive are marred. Thus, it is preferable to determine the quantity ofthe glass to be mixed with the adhesive to 100 to 500 parts by weightper resin of 100 parts by weight regardless of the components of amixture.

The weight of the present invention can be produced in such the same wayas any other conventional adhesive of this type and applied for arotating body such as a rotor in a motor of a brushless outer rotor typeor a brush motor and a polygon mirror for use in a laser printer.

PREFERRED MODES FOR EXECUTING THE INVENTION

One embodiment of the present invention will be described hereinafter.

EMBODIMENTS 1 and 2

A weight composition was prepared by combining ultraviolet curing resinof urethane acrylates (trade name "TB3042C" made by Three Bond Co.,Ltd.) with soda glass beads having a specific gravity of 2.5 and a grainsize of 45 μm or less (trade name "GB731B" made by Toshiba BallotiniCo., Ltd.), soda glass beads having a specific gravity of 2.5 and agrain size of 106 to 250 μm (trade name "GP105A" made by ToshibaBallotini Co., Ltd.), glass beads of TiO₂ --BaO--SiO₂ having a specificgravity of 4.3 and a grain size of 53 to 74 μm (trade name "HGB253" madeby Toshiba Ballotini Co., Ltd.), and silica powder (disordered in shape)having a specific gravity of 2.5 and a 100 mesh in grain size (tradename "CRYSTALLITE MESH 100") in the combining proportion (part byweight) shown in Table 1 below. The weight composition thus obtained wasfilled in a cylinder of polyethylene in the state shielded completelyfrom light and hardened on exposure to ultraviolet rays with accumulatedlight volume of 3000 mJ/cm². Then, the specific gravity and thickness ofthe weight hardened like a film layer were measured.

                                      TABLE 1                                     __________________________________________________________________________                             Comparative                                                                          Comparative                                                                          Comparative                                                                          Comparative                              Embodiment 1                                                                          Embodiment 2                                                                          Example 1                                                                            Example 2                                                                            Example 3                                                                            Example 4                       __________________________________________________________________________    TB3042C  100     100     100    100    100    100                             GB731B   250     200                                                          GP105A   100     100                                                          CRYSTALLITE                     150    350                                    100 MESH                                                                      HGB253           100                          350                             Gravity  1.80    2.13    1.10   1.62   Unmixable                                                                            2.60                            Thickness                                                                              4.2     2.3     4.5    2.4    Unmixable                                                                            0.5                             of Hardened                                                                   layer (mm)                                                                    __________________________________________________________________________

The specific gravity shown in Table was measured at 25° C. by use of aspecific gravity cup after subjecting the specimen to vacuum degassing.

The thickness of the hardened part of the weight separated from the partremaining in its gel state, which was obtained in such a manner that theweight composition was filled in the cylinder of polyethylene having adiameter of 7 φmm in the state shielded from light and hardened onexposure to ultraviolet rays with accumulated light volume of 3000mJ/cm² was measured by use of a micrometer.

As is clear from the experimental result mentioned above, the weightcomposition (Embodiment 1 or 2) obtained by combining ultraviolet curingresin (TB3042C) with soda glass beads (GB731B and GP105A) or glass beadsof TiO₂ --BaO--SiO₂ (HGB253) is higher in specific gravity and larger inhardened layer thickness than comparative compositions (ComparativeExamples 1 to 4) made by combining ultraviolet curing resin (TB3042C)with silica powder disordered in shape (trade name "CRYSTALLITE MESH100").

As is apparent from the foregoing, since the weight compositionaccording to this invention can be obtained by combining ultravioletcuring resin with one or more solid spherical powders selected fromsilicated glass, boro-silicated glass and phosphate glass which are highin permeability of ultraviolet rays so as not to exert a bad influenceupon curing of the ultraviolet curing resin, it can be hardened in ashort time only by being exposed to ultraviolet rays without need for aheating process.

Furthermore, according to this invention, the weight adhesive, even theinner part thereof, can be sufficiently hardened without remaining anunhardened part of the adhesive. Even when the aforenoted solidspherical powder is filled densely, the powder particles can beintimately bonded with one another through the adhesive resin, so that aweight having high specific gravity can be obtained for suitablyadjusting the balance of a rotating body.

INDUSTRIAL APPLICABILITY

Thus, the weight composition of this invention, which is applicable fora rotating body such as a rotor in a motor of a brushless outer rotortype or a brush motor and a polygon mirror for use in a laser printer,can be manufactured by a shortened manufacturing line without need for aheating process.

I claim
 1. A weight for adjusting the balance of a rotating body,comprising:an ultraviolet curing resin; a spherical powder constitutedof at least one powdered glass selected from the group consisting ofsilicate glass, boro-silicate glass and phosphate glass, said sphericalpowder having a specific gravity of 0.2 or more; and a spherical powderconstituted of at least one glass powder selected from the groupconsisting of TiO₂ --BaO--SiO₂, BaO--ZnO--SiO₂ and lead glass.